Rapidly variable capacity absorption refrigeration system



May 23, 1967 J. s. SWEARINGEN RAPIDLY VARIABLE CAPACITY ABSORPTIONREFRIGERATION SYSTEM Filed April 19, 1966 wm Wm I I l I II l I I l l I Iliillinullnllinl duuso/v S. SWEAR/NGf/V I N VENTOR.

United States Patent 3,320,760 RAPIDILY VARIABLE CAPACITY ABSORPTIONREFRIGERATION SYSTEM Judson S. Swearingen, 2235 Carmelina Ave., LosAngeles, Calif. 90064 Filed Apr. 19, 1966, Ser. No. 543,749 Claims. (Cl.62-141) This invention relates to an absorption refrigeration system andparticularly to one in which the output of refrigeration may be changedvery rapidly to accommodate rapid variations in requirements forrefrigeration.

The system provided by this invention is particularly applicable toabsorption refrigeration in which both the absorbent and the refrigerantare liquids at normal pressures and temperature and in which the spentabsorbent is separated from the refrigerant by distillation. Theinvention has special applicability in systems wherein the distillationis carried out in a multiple effect system. However, it is not limitedto these specific applications as will hereinafter appear.

In conventional absorption refrigeration systems the refrigeration isgenerated by evaporation of the refrigerant as it flows over a bank oftubes in an evaporator, and the refrigeration serves to cool thecontents of such tubes. The most common arrangement i to provide suchtubes and arrange them so as to conduct therethrough a fluid medium suchas water, or in the event of a lower temperature requirement, a lowerfreezing liquid such as brine, so that such fluid medium will be cooledby the refrigeration. The vapor liberated by the evaporation is absorbedby the absorbent liquid as such liquid is introduced into an absorberand is permitted to flow downwardly over another set of coils or bank oftubes through which a cooling medium is normally caused to flow. Bothbanks of tubes are generally located in the same vessel so that it maybe said that the evaporator and the absorber are in free communicationwith one another. The spent absorbent (spent in that it is partly orcompletely saturated with refrigerant) drains to the bottom of thevessel and is returned to the regeneration section of the system whereit is regenerated by the application of heat resulting in thedistillation of the refrigerant content thereof, the refrigerant contentthereby passing off as a Vapor and being collected and condensed forreuse.

The most common way of controlling a system of this kind as to theamount of refrigeration which it produces is by controlling the amountof heat applied to the regenerator in which the refrigerant is distilledfrom the spent absorbent. Controls have also been applied to regulatethe rate at which the spent absorbent is returned from the absorber tothe regenerator or distillation portion of the system.

In the so-called multiple effect distillation employed in such systemsheat is applied to the spent absorbent in a first effect heater while itis under substantially higher pressure than prevails in a second effectcondenser. The resulting vapor from this first effect heater wheredirect heat is applied, condenses in a steam heated still wherein itsupplied the heat to further boil the absorbent which is partiallyregenerated in the first effect heater. In this steam heated still thepartially regenerated liquid absorbent is at a substantially reducedpressure so that it will boil under the heating action of the condensingsteam. The vapor from the second effect heater condenses in the secondeffect condenser.

When control of the system is effected by controlling the heat input tothe first heating zone there is a great lag in response making thesystem quite unstable and if the control is effected by a switching onand off of the heating supply, then there is always either overheatingor insufficient heating. Control of flow of the spent absorbent requiresexactitude of regulation or it likewise will result in insufficientheating or excessive regeneration.

It is therefore an object of this invention to provide a system ofabsorption refrigeration in which the temperature and the quantity ofrefrigeration produced are controlled by controls which are immediatelyresponsive and in which the system operates at a high efliciency over awide capacity range.

Another object is to provide such a system which may be caused to changefrom a low rate or zero rate of refrigeration production to productionof its maximum capacity of refrigeration without any practical time lag.

Another object is to provide such a system in which the spent absorbentis most efficiently regenerated.

Another object is to provide such a system in which the spent absorbentwill be efficiently regenerated but in which the rate of regeneration isnot required to correspond to the rate of refrigeration at any giventime.

Another object is to provide such a system in which the maximum rate ofheat input for regeneration may be begun at any time and without anysubstantial delay.

Another object is to provide such a system in which the heat input willbe into a non boiling liquid to provide a favorable heat transfer rateand produce the lowest feasible corrosion rate of the heating vessel.

Another object is to provide such a system in which the temperature towhich the absorbent is subjected in the absorber may be preciselyregulated'so that it will not reach the freezing point of the absorbentyet will so closely approach such freezing point as to provide thelowest possible temperature in the evaporator and hence provide for thegreatest efficiency of heat transfer to a fluid medium being cooled bysuch refrigeration.

Other objects and advantages of this invention will become apparent fromthe following description taken in connection with the accompanyingdrawings wherein is set forth by way of illustration and example oneembodiment of this invention.

In the drawing:

The single figure is a diagrammatic illustration of an absorptionrefrigeration system embodying the present invention.

In the embodiment illustrated in the drawing which will be described inmore detail hereinafter provisions are made for the storage ofsubstantial quantities of refrigerant in liquid form ready to beintroduced into an evaporator for producing refrigeration at such rateas may be required by any demands that may be made upon the system forrefrigeration up to the full capacity of the system whether such demandsbe sudden or gradual, and for the storage of a substantial amount ofabsorbent fully regenerated and ready for introduction into the absorberto control the pressure and hence the temperature at which refrigerationis produced. The maintenance of such stored quantities of refrigerantand absorbent ready for use not only make possible the immediate meetingof such demands as may be made upon the system, but also render itunnecessary that the rate of regeneration be immediately increased to arate comparable to that at which refrigeration is demanded. Regenerationmay therefore be conducted at a more efficient rate and changes in therate of refrigeration may be made more gradually.

In the regeneration of absorbent in accordance with this invention theapplication of external heat is so regulated as to maintain theabsorbent in the zone being heated at a constant temperature and thistemperature is so regulated as to be sufficiently high to properlyregenerate any incoming spent absorbent. The constant temperature somaintained should be low enough so that it will not boil the at leastpartially regenerated absorbent present therein, but high enough so thatwhen spent absorbent is introduced into such body of partiallyregenerated absorbent the refrigerant therein will be vaporized anddriven off. The body of partially regenerated absorbent in such heatingzone will be kept great enough with respect to the maximum expected rateof introduction of unregenerated absorbent that the introduction of suchunregenerated absorbent at the maximum expected rate willvnot besufficient to lower the temperature of the Whole body of absorbent insuch regenerating zone to a temperature below the point at which therefrigerant therein will vaporize, for a period of time required forefficient increasing of the rate of heating to compensate for theintroduction of the spent absorbent.

The vaporization of refrigerant is preferably carried out in such a waythat it acts as a vapor lift type of pump to circulate the hot liquid inthe regenerator. The vapor thus produced passes into the disengagementzone along with a proportionate amount of heatedvliquid absorbentsubstantially half regenerated. The amount of heat applied to theheating zone of the regenerator is controlled automatically by thetemperature within such zone to maintain such temperature constant.

By this means a constant temperature is immediately available in theheating zone for initial distillation or partial distillation of spentabsorbent entering the heating zone. At the same time, the heat requiredfor distillation is put into a nonboiling liquid which is preferablefrom the standpoint of heat transfer rate and of minimum corrosion ofthe heating vessel.

It is desirable that the heat exchangers and the abovementioned heatingzone of the regenerator receive the spent absorbent at a graduallyincreasing rate rather than in a sudden surge when a sharp increase inrefrigeration is called for. This is accomplished in the structure shownin the drawing by providing a pumping mechanism for pumping the spentabsorbent preferably slowly at first but at an increasing rate from thebottom of the absorber toward the regenera-tor. The rate of pumping iscontrolled by the accumulationof spent absorbent in the bottom of theabsorber so as to be greater when the quantity of absorbent is greaterand slower when the quantity of absorbent in the absorber drops.

It is, of course, desirable to have the temperature at whichrefrigeration is produced in the evaporator as low as possible so as tocreate as much temperature difference as possible between suchevaporator and the fluid medium being circulated in heat exchangerelation thereto in order that the heat exchanger costs may be kept aslow as possible. On the other hand, this temperature must not be allowedto drop to the freezing point of the absorbent. The temperature iscontrolled in the illustrated embodiment by controlling the flow ofabsorbent into the absorber so as to maintain the pressure in theevaporator constant at a predetermined value.

On the other hand, the amount of refrigeration produced may becontrolled by increasing or decreasing the flow of refrigerant to theevaporator as the temperature in the fluid medium being circulated inheat exchange relation to the evaporator rises or falls, such regulationbe ing preferably of such a nature as to maintain the temperature ofsuch fluid medium leaving the evaporator substantially constant at apredetermined value.

Referring more in detail to the drawing:

A coil 1 is provided for circulating a fluid medium such as water orbrine through an evaporator or evaporation zone wherein a spray 2 ofliquid refrigerant is released over the coil 1 under pressure conditionslow enough to cause evaporation of the refrigerant from the coilsurfaces and thereby produce refrigeration, when the temperature of thefluid medium in such coil is above a predetermined value. Because of theheat exchange relation between the fluid in the coil 1 and therefrigerant on the exterior thereof, such refrigerant will take up heatfrom the fluid medium within the coil and be evaporated therebyresulting in lowering of the temperature of such fluid whereupon it willbe Withdrawn as in i t by the arrows on the coil 1 and conducted to apoint where it may be used for whatever purpose it was intended. Theevaporator is contained within a closed vessel 3 and within this closedvessel preferably somewhat below the evaporator section within which thecoil 1 and the spray 2 are located there is a cooling coil 4 throughwhich some type of coolant may be circulated in order to remove someheat from the zone within which the spray 5 introduces a fresh absorbentinto the vessel 3. This absorbent will abs-orb the vapor resulting fromevaporation of refrigerant from the, spray 2 and the coolant in the coil4 will serve to remove the heat of absorption. The absorbent havingthu-s absorbed the refrigerant vapor will collect in a pool 6 in thelower portion of the vessel 3 from which itmay be withdrawn through adrain pipe 7 by means of a pump 8 and forced through a pipe 9 to heatexchangers 10 and 11 through which it passes successively and in whichit will be somewhat warmed through heat exchange with regeneratedabsorbent as presently to be described. It then passes through the line12 and into the column 13 in which, in accordance with this invention,there will be maintained a large volume of hot partially regeneratedabsorbent. The temperature of the partially regenerated absorbent in thecolumn 13 will be maintained sufiiciently high that when the spentabsorbent enters the column the refrigerant absorbed therein will boiland be released as refrigerant vapor. This release of vapor which occursas illustrated far beneath the surface of the liquid in the column 13,will act as a vapor pump within the column 13 and as the vapor risesinto the chamber 14 above the column 13 it will carry with it some ofthe liquid absorbent from the column 13.

In the chamber 14 most of the refrigerant vapor will be disengaged fromthe liquid absorbent and will flow over through the passageway 15 abovethe partition between the chambers 14 and 16 and into the chamber 16.The liquid absorbent thus disengaged from the vapor in chamber 14 willflow back into the heater portion of the regenerator' through theconduit 17. It is noted that the upper end of the walls of the column 13extend somewhat above the bottom of the chamber 14 so that such liquidas falls back into the bottom of the chamber 14 cannot run back into thecolumn 13 but must instead flow through the passageway 17 into the spacein which heat is being added from the outside as will be presentlydescribed.

A small portion of the liquid entering the chamber of the chamber 16.The partially regenerated liquid will not be permitted to excessivelyaccumulatein the chamber 16. This quantity is controlled asvby a floatoperated valve 18 whereby the liquid will be permitted to flow out asfast as it comes into the chamber 16. It will flow out through the line19 into the heat exchanger 11 wherein it will flow countercurrently withrespect to the spent absorbent passing through this heat exchanger ashereinbefore described and will serve to heat the spent absorbent in thecourse of such passage while this liquid from chamber 16 still remainsat very nearly the pressure prevailing in chamber 16. The partiallyregenerated, partially cooled absorbent will then leave the heatexchanger 11 through a line 20, in which the valve 18 is located, andpass through a coil 21 and int-o a chamber 22. Having beencooled inexchanger 11 this liquid from chamber 16 will not boil significantlyunder the very considerable pressure reduction which it undergoes inpassing through valve 18. However, it will, as a result of such pressurereduction be in condition to be boiled by the heat from the first effectvapor which will contact coil 21 and be condensed thereon in chamher 27as it provides second effect heat to the absorbent in coil 21. The vaporspace in the chamber 22 communicates through a passage 23 above apartition between the chamber 22 and the chamber 24 and in the chamber24 there is located a cooling coil 25 through which cooling water orother cooling medium is caused to flow. The cooling thus produced by thecooling coil 25 will serve to maintain by condensation of refrigerantvapor the partial pressure of any refrigerant vapor in the chamber 24and thus the pressure therein and therefore that in the chamber 22 andthe inside of the coil 21 will be quite low. Such vapor will have beenliberated from fully regenerated absorbent so the absorbent, which hasan affinity for the refrigerant vapor, must necessarily have been at amuch higher temperature than condensing refrigerant at the samepressure.

Referring again to the chamber 16 wherein the refriger-ant vaporproduced in column 13 is fully disengaged from liquid, the vapor, stillat the high pressure prevailing in chamber 16, passes therefrom througha passage 26 over the partition between the chamber 16 and a chamber 27,and into chamber 27 wherein the coil 21 is located. The coil 21, havingpartially cooled regenerated absorbent flowing inside of it at therelatively lower pressure to which it was reduced by the valve 18, isthe only heat absorbing element in the vapor space communicating withthe chamber 16. Refrigerant vapor continually rises into the chamber 16and increases the pressure therein until it is sufficiently high that itwill condense at the temperature of the outside of the coil 21, therebyheating the partially regenerated absorbent in the coil 21 while therefrigerant vapor condenses on the outside surface of this coil whilethe partially regenerated liquid inside the coil boils.

Liquid thus condensing on the coil 21 will fall to the bottom of thechamber 27 and flow out through the line 28 into the chamber 24 where itwill join the condensed refrigerant which will have condensed on thecoil 25 in that chamber.

The pressure in the chamber 27 and the chamber 16 being much higher thanthat in chamber 22 for reasons heretofore stated, the partiallyregenerated liquid absorbent in the bottom of the chamber 16 will flowthrough the valve 18 when the same is opened, having freely reached itthrough heat exchanger 11 it then flows through line 20. The pressuredownstream from the valve 18 will be only slightly above that prevailingin the chamber 22, differing therefrom only by the amount of thepressure drop through the coil 21.

The partially regenerate-d absorbent inside of the coil 21 will thusfreely boil and liberate the remainder of the absorbed refrigerant asthe vapor condenses on the outside of this coil. Thus the absorbentwithin the coil becomes fully regenerated but with some refrigerantvapor entrained therein and this mixture of liquid and vapor isdischarged into chamber 22 wherein the vapor is fully disengaged andflows through the pasage 23 into the chamber 24 to condense on thesurface of the condenser coil 25. Thereafter it falls and accumulates inthe bottom of the chamber 24. The fully regenerated absorbent willaccumulate in the bottom of the chamber 22.

As refrigeration is required, refrigerant will flow out of chamber 24through the line 29 and into the sprays 2 from which it is distributedon the outer surfaces of the evaporator coil 1 to cool the water orother fluid medium circulating therein. The refrigeration requirement isnormally determined by the temperature of the circulating medium such aswater within the coil 1. A temperature sensing element 30 is located intemperature sensing relation to the outflow from coil 1 and connected tocontrol the valve 31 which in turn controls the flow of refrigerant fromthe chamber 24 onto the evaporator coil 1. As refrigerant evaporates onthe outer surfaces of the coil 1 vapor in large volume is formed insidethe chamber 3 thereby increasing the pressure inside of chamber 3. Sincepressures for control purposes.

the pressure inside of chamber 3 determines the temperature at whichvaporization of refrigerant will take place, the refrigerant vapor thusformed must be removed in order to keep the evaporator temperature downto the point desired. To accomplish this absorbent is delivered from thechamber 22 through a line 32, through heat exchanger 10 wherein itcountercurrently heats spent absorbent from the evaporator chamber 3 andis itself cooled. The heat exchanger 10 has a relatively large mass andheat capacity so that flow of countercurrent streams therein need not besimultaneous. This cool regenerated absorbent then flows through theline 33 and through sprays 5 onto the outer surfaces of the cooling coil4. On such surfaces it is exposed to the refrigerant vapor inside thechamber 3 and absorbs the vapor, thereby keeping the pressure inside ofchamber 3 lower than it otherwise would be. The regenerated absorbentbecomes spent by this absorption and falls to the bottom of the chamber3.

The rate of flow of regenerated absorbent onto the coils 4 necessary tomaintain the predetermined desired low pressure and hence apredetermined temperature of refrigeration on the coil 1, is controlledby the valve 34 which in turn is controlled by a pressure sensingelement 35 exposed to the pressure within the evaporator chamber 3. Thesensor 35 and the valve 34 are so adjusted that when the pressure withinthe evaporator chamber 3 tends to rise and this is sensed by the sensor35, the valve 34 will open to permit more absorbent to flow through thespray 5, thereby reducing such pressure. These will be set to keep thepressure within the chamber 3 at a substantially constant predeterminedvalue so as to maintain the temperature on the coil 1 at substantiallyconstant predetermined value. This temperature should be determined bymaking it as low as possible while keeping it above the freezing pointof the refrigerant. In case of the use of water as a refrigerant, whichis frequently done, the temperature should be some 3 or 4 degrees abovethat of the freezing point of water, or approximately 36 or 37 degreesFahrenheit. The vapor pressure of water of 32 degrees Fahrenheit being4.6 millimeters of mercury absolute and that at 37 degrees being 5.6millimeters, this relatively low temperature difierential above thefreezing point of water will provide a very satisfactory ratio of Itwill be understood, however, that the system is not limited to the useof water as a refrigerant as some other substances, well known asrefrigerants may be employed, along with substances respectivelysuitable as absorbents therefor. However, when water is used as arefrigerant a suitable absorbent is lithium bromide solution in water inconcentration between 58% and 64%, by weight, with a variation between4% and 5% between spent and regenerated condition. Thus when spent thepercentage of lithium bromide might, for example, be 58% and whenregenerated 62%.

In the event of the use of refrigerant and absorbent from the stored upsupplies in chambers 24 and 22 at a temporarily very high rate and onehigher than the current rate of regeneration of absorbent, the levels inchambers 22 and 24 will begin to drop and a substantial quantity ofspent absorbent will begin to accumulate in the bottom of the chamber 3at a correspondingly high rate. As the level of this spent absorbentrises in the bottom of chamber 3 it Will actuate the float in thatchamber and cause the pump 8 to begin building up its rate of pumpingand within a time of the order of a minute or two the systern should beable to deliver regenerated absorbent and condensed refrigerant into thestorage chambers 22 and 24 at substantially the rate of withdrawaltherefrom. Meanwhile, however, the sudden requirement for refrigerationwill have been met without delay. The inventories in chambers '22 and 24should be sufficient to last for a time sufiicient for the regenerationto catch up to the rate of usage, which will of course vary according tothe design of and requirements from the system. Normally a one or twominute supply in chambers '22 and 24 for the highest expected rate ofuse should be sufficient.

One of the reasons why the system thus described can fairly quicklybegin to deliver regenerated streams to the respective chambers 22 and24 is found in the heating furnace 36. This furnace consists of an outershell 37 with an inner heating surface 38 heated by hot gases passingtherethrough and originating in the burner 39. The annular space 40between the outer shell 37 and the heating surface 38 is maintained fullof partially regenerated absorbent liquid. This space is connectedthrough communicating lateral conduits 41 and 42 with a large verticalcolumn 13 previously mentioned which is likewise filled with the samebody of hot partially regenerated absorbent liquid. These largepassageways 41 and 42 permit free thermal convection or temperatureinduced flow between the column 13 and the annular space 40 so thatthese remain at substantially the same temperature and this temperatureis determined by the setting of the temperature controller 43 as biasedby a pressure controller 43a exposed within the chamber 14, whichactuates a valve 44 in the fuel line to the burner 39. The reason forthe pressure controller 43a arises out of the fact that under varyingconditions of operation the pressure in chambers 14 and 16 and hencethat at any. point Within the body of liquid in furnace 36 varies.Hence, if the temperature were maintained constant without reference tosuch pressure, the constituency of this body of liquid would vary withvariations in pressure. Since it is desirable to keep this constituencythe controller 43a is provided to suitably bias the temperaturecontroller 43 to compensate for pressure variations. By these means thetemperature of the liquid in the annular space and in the column 13ismaintained at a desired constant temperature subject however to biasto correct for pressure variations .and consequently at a desiredconcentration.

When liquid accumulates in the bottom of the shell 3 and is delivered bythe pump 8 to the column 13 well below the surface. of the liquid thespent absorbent so delivered boils at a lower temperature than that ofthe partially regenerated absorbent in the column-13 and upon enteringimmediately flashes and liberates its equivalent portion of absorbedrefrigerant as vapor in the form of bubbles which rise upward in column13. This causes rapid upflow in column 13 and increases the rate ofcirculation through passageways 41 and 42 and the annulus '40 andimproves the heat transfer rate on the heating surface 38.

The heater thus described has the advantage of self circulation, ofbeing immediately ready to deliver any reasonably required quantity ofheat to the incoming spent absorbent, and of receiving the heat from thesurface 38 without boiling.

It is possible for small amounts of fixed gas to get into the chamber 3by small leaks or through chemical action such as corrosion whichliberate fixed gas. This interferes with the rate of absorption ofrefrigerated vapor on the surface of the coil 4 and such gas must beremoved. A convection barrier 45 is employed to partition off a zoneinside of the chamber 3 which includes a portion of the absorbingsurface on the coil 4 and because of the absorption of vapor inside ofthe zone created by the barrier 45 there will be a flow of vapor intothat chamber. This flow is so arranged that it sweeps all of the coils 4which are not inside of the zone and thereby sweeps away any gas intheir vicinity away from such coils and into the aforesaid zone. Gascollected in such zone flows along with the absorbent 6 into the pump 8and eventually passes over into the chamber 27 along with the vapor fromthe first effect heating and in this chamber such vapor is condensed onthe surface of coil 21.

A similar convection barrier 46 is placed inside the chamber 27 to forman enclosed zone in the upper part thereof which contains a portion ofthe condensing surface of the coil 21. This acts to draw a portion ofthe vapor coming into the chamber 27 across the unenclosed portion ofthe coil 21 and this sweeps any fixed gases off of that surface andthrough the barrier along with the vapor which may condense on theportion of the coil 21 which is inside of the enclosed zone. Thus all ofthe fixed gas will be brought into the zone above the barrier 46 fromwhich it may be withdrawn through a line 47. with a small portion of therefrigerant vapor. It is drawn from the line 47 by a vacuum pump 48 andrejected to the atmosphere but the line 47 is provided in its verticalportion with air cooling fins 49 or other similar devices which serve toradiate heat and cause condensation therewithin of most of therefrigerant vapor, which then flows back by gravity into the chamber 27.

The requirements of systems such as described are such that the boilingpressure in chambers 14, 16 and 27 when using water as a refrigerant areof the order of 5 to 20 pounds per square inch absolute. The vacuum pump48, therefore, must have the characteristic of pumping against anegative as well as a positive head so as to prevent excessivequantities of vapor from leaving the system should the pressure insideof the chamber 27 be above atmospheric pressure.

From the foregoing it will be seen that that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the method.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood thatall matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. In an absorption refrigeration system which comprises a regeneratedabsorbent reservoir, a regenerated liquid refrigerant reservoir, anevaporator and absorber in open communication with one another, firstand second conduit means connecting said refrigerant. reservoir to saidevaporator and said absorbent reservoir to said absorber, respectively,a regenerator, third conduit means connecting said absorber to saidregenerator to conduct spent absorbent to said regenerator, and meansconnected to said regenerator for receiving absorbent and refrigerantfrom said regenerator and separating and cooling same and deliveringthem to said reservoirs respectively, the improvement which comprises anautomatic flow controller in one of said first and second conduit meanshaving a sensing control element exposed to a portion of the interior ofthe system affected by the refrigeration produced in the evaporator forsensing a condition in said portion significant of the refrigerationproduced in said evaporator, whereby flow of one of said absorbent andrefrigerant to said intercommunicating evaporator and absorber may becontrolled by said condition to thereby control the refrigerationproduced in said evaporator and maintain said condition withinpredetermined desired values.

2. An absorption refrigeration system as set forth in claim 1 in whichsaid flow controller is in-the conduit between the absorbent reservoirand the absorber and said sensing control element is a pressure sensingelement located to sense the pressure in said evaporator.

3. An absorption refrigeration system as set forth in claim 1 in whichthere is a fluid medium circulating means in heat exchange relation tosaid evaporator to cool such of said fluid medium emerging from saidheat exchange relation with said evaporator.

4. An absorption refrigeration system as set forth in claim 1 in whichthe regenerator comprises a vessel adapted to contain absorbent, meansfor applying heat to a body of absorbent in said vessel at a rate tomaintain its temperature within a range below the boiling point of theabsorbent and above the boiling point of the refrigerant being used.

5. An absorption refrigeration system as set forth in claim 4 incombination with means for adjusting said rate of applying heat so as tomaintain said temperature within said range during the highest expectedrate of addition of spent absorbent to said regenerator.

6. An absorption refrigeration system as set forth in claim 5 in whichsaid means for adjusting the rate of applying heat includes atemperature sensor exposed to the absorbent adjacent the point ofintroduction of spent absorbent into said regenerator and adapted toincrease the rate of heat addition when temperature at such point fallsbelow a predetermined minimum and decrease the rate of heat additionwhen the temperature at such point exceeds a predetermined maximum.

7. An absorption refrigeration system as set forth in claim 4 in whichthe absorbent capacity of said regenerator relative to the greatestexpected surge of spent absorbent thereto and the time required forincreased application of heat from the minimum to the maximum rate issufiiciently large that the largest anticipated surge of spent absorbententering into said regenerator when the same is full of partlyregenerated absorbent at a temperature just below its boiling point willnot result in lowering the temperature of the resultant body ofabsorbent below the boiling point of the refrigerant within theregenerator within the time required for the maximum rate of applicationof heat to the regenerator to begin.

8. An absorption refrigeration system as set forth in claim 4 in whichsaid regenerator has a portion normally filled with hot liquid absorbentand said portion is shaped to provide a circulating path for suchabsorbent, and in which said means for applying heat is located to applyit to a portion of said circulating path.

9. An absorption refrigeration system as set forth in claim 5 in whichthe point of introduction of spent absorbent into said regenerator isbelow the normal level of liquid absorbent in said regenerator.

10. An absorption refrigeration system as set forth in claim 9 in whichsaid regenerator has a portion normally filled with hot liquid absorbentand shaped to provide a circulating path therefor, said means forapplying heat is positioned to apply it to a portion of said path, andin which the point of introduction of spent absorbent into saidregenerator is in a portion of said circulating path remote from theportion to which said heat is applied.

References Cited by the Examiner UNITED STATES PATENTS 2,650,480 9/1953Gilmore 6214l X LLOYD L. KING, Primary Examiner.

1. IN AN ABSORPTION REFRIGERATION SYSTEM WHICH COMPRISES A REGENERATEDABSORBENT RESERVOIR, A REGENERATED LIQUID REFRIGERANT RESERVOIR, ANEVAPORATOR AND ABSORBER IN OPEN COMMUNICATION WITH ONE ANOTHER, FIRSTAND SECOND CONDUIT MEANS CONNECTING SAID REFRIGERANT RESERVOIR TO SAIDEVAPORATOR AND SAID ABSORBENT RESERVOIR TO SAID ABSORBER, RESPECTIVELY,A REGENERATOR, THIRD CONDUIT MEANS CONNECTING SAID ABSORBER TO SAIDREGENERATOR TO CONDUCT SPENT ABSORBENT TO SAID REGENERATOR, AND MEANSCONNECTED TO SAID REGENERATOR FOR RECEIVING ABSORBENT AND REFRIGERANTFROM SAID REGENERATOR AND SEPARATING AND COOLING SAME AND DELIVERINGTHEM TO SAID RESERVOIRS RESPECTIVELY, THE IMPROVEMENT WHICH COMPRISES ANAUTOMATIC FLOW CONTROLLER IN ONE OF SAID FIRST AND SECOND CONDUCT MEANSHAVING A SENSING CONTROL ELEMENT EXPOSED TO A PORTION OF THE INTERIOR OFTHE SYSTEM AFFECTED BY THE REFRIGERATION PRODUCED IN THE EVAPORATOR FORSENSING A CONDITION IN SAID PORTION SIGNIFICANT OF THE REFRIGERATIONPRODUCED IN SAID EVAPORATOR, WHEREBY FLOW OF ONE OF SAID ABSORBENT ANDREFRIGERANT TO SAID INTERCOMMUNICATING EVAPORATOR AND ABSORBER MAY BECONTROLLED BY SAID CONDITION TO THEREBY CONTROL THE REFRIGERATIONPRODUCED IN SAID EVAPORATOR AND MAINTAIN SAID CONDITION WITHINPREDETERMINED DESIRED VALUES.